Method and installation for making flour from ozone-treated grains

ABSTRACT

The present invention relates to a method for making flours having a high food safety level comprising the grinding of grains previously cleaned and moistened, characterized in that, prior to or simultaneously with said grinding, said grains are brought into contact with ozone produced from a carrier gas, preferably in a quantity of between 0.5 and 20 expressed in grams of ozone per kilo of grains.

[0001] The subject of the present invention is a novel method for makingflours intended for human consumption or as animal feed and having ahigh food safety level.

[0002] It also relates to a specific installation suitable for carryingout this method.

[0003] The invention finds in particular application in the field ofindustrial milling, specialized milling, in the production of specificflours as well as in the industrial making of bakery products and ofanimal feed.

[0004] It is known that grains obtained in particular from cereals andintended for the production of flours have, before milling, when theyare used in the natural state, a number of contaminants of telluricorigin, or resulting from contamination during storage.

[0005] These contaminants are generally situated at the periphery of thegrains and exist in the form of microbes, bacteria, pesticide residues,mycotoxins and various spores.

[0006] During the milling phase, the contaminated peripheral tegument isbrought into intimate contact with the flour obtained by grinding theinner part of the grain. During this operation, the peripheralcontamination therefore contaminates the flours, which results inproblems of food safety, preservation, and use, which, in some cases,can make the flours thus obtained unfit for consumption.

[0007] Milling industries, whether nonindustrial or industrial, arenowadays confronted with problems of contamination and various solutionshave been recommended for remedying them.

[0008] Thus, it has been proposed to subject the grains before milling:

[0009] either to a physical treatment by ionization;

[0010] or to a chemical treatment, in particular with hydrogen peroxide.

[0011] However, these two techniques have various disadvantages whichhave prevented their generalized use.

[0012] Indeed, ionization involves the use of radioactive sources whichare perfectly controlled, and geographically sited at appropriate siteswhich do not correspond to the sites of production of the flours. Theresulting cost of transportation, which adds to the cost of treatmentproper, makes ionization extremely expensive and constraining, such thatits use remains limited to a few very specific uses involving very smallquantities of grains.

[0013] Moreover, chemical treatment of the grains with hydrogen peroxideis not perfectly satisfactory since it is accompanied by bacterialreviviscence after treatment and requires, because of the nature of thisreagent, special precautions during use and a control which is hardlycompatible with the use envisaged.

[0014] Chemical agents other than hydrogen peroxide have also beenenvisaged for decontamination treatments of grains, among which theremay be mentioned:

[0015] chlorine and chlorine-containing agents, whose recentlydemonstrated mutagenic and carcinogenic properties in fact limit the usethereof;

[0016] peracetic acid whose use causes a reduction in the organolepticqualities of the grains and requires a controlled use which is hardlycompatible with the use envisaged.

[0017] It is known, moreover, that the ozone produced from carriergases, which can be either atmospheric oxygen, pure oxygen or a mixtureof the two in variable proportions, has sterilizing properties whichhave been widely exploited in the treatment of water intended for humanconsumption, as well as in an industrial setting (fish farming,shellfish farming, pharmacy and fine chemistry).

[0018] The use of ozone was also recommended in particular in patent FRNo. 93 11776 in the context of the treatment of seeds and of bulbs, butonly with the aim of improving germination.

[0019] Under these conditions, the aim of the present invention is tosolve the technical problem consisting in providing a novel method formaking flours having a high food safety level which can be relativelyeasily used directly at the sites of manufacture and regardless of thequantities of grains to be treated, while preserving the technologicalqualities of the flours necessary in particular in breadmaking.

[0020] It has been discovered, and this constitutes the basis of thepresent invention, that it was possible to decontaminate grains beforemilling and even to very significantly improve the qualities of theflours obtained by grinding these grains, as well as the qualities ofthe by-products, by prior treatment of said grains with ozone producedfrom a carrier gas, without the use of additional treatment agents, andunder conditions of implementation, in particular of duration, which arecompatible with a continuous industrial use.

[0021] Thus, according to a first aspect, the subject of the presentinvention is a method for making flours having a high food safety levelcomprising the grinding of grains previously cleaned and moistened,characterized in that, prior to or simultaneously with said grinding,said grains are brought into contact with ozone produced from a carriergas, preferably in a quantity of between 0.5 and 20 expressed in gramsof ozone per kilo of grains.

[0022] This method makes it possible to solve, for the first time and ina completely satisfactory manner, the problem of the contamination offlours with which milling industries are confronted.

[0023] It is known in milling techniques, that to obtain good grinding,it is necessary to moisten the grains before carrying out the millingoperation. This moistening is up until now carried out with untreatedwater and the moistening phase is generally followed by a rest phaseduring which the development of the strains present is further promotedbecause of the moisture provided.

[0024] According to a particular characteristic of the method inaccordance with the invention, the water serving for moistening thegrains is treated beforehand with ozone.

[0025] It has indeed been observed that this prior treatment with ozoneof the water serving for moistening the grains made it possible tofurther improve the beneficial effects observed by the sole prior drytreatment of the grains and to surprisingly avoid the reviviscence ofthe strains present at the periphery of the tegument during theabovementioned rest phase.

[0026] It has also been observed, unexpectedly, by conventionalbreadmaking tests, that the doughs made from flour obtained from grainswhich have undergone this prior treatment had improved characteristicswhich are particularly suitable for making sweetened products of theEnglish or Genoese fruitcake type, of the mixed type for coating(donuts, breadcrumb dressing, and the like) and of industrialbreadmaking products.

[0027] A second subject of the invention therefore consists in the useof the flour thus treated for the making of these products.

[0028] This particular use of the method in accordance with the presentinvention, combining a dry treatment and a wet treatment of the grainsbefore milling constitutes a currently preferred embodiment of theinvention.

[0029] According to a particular characteristic of the method inaccordance with the invention, the period for which the grains arebrought into contact with the ozone is between 5 and 70 min, andpreferably between 15 and 40 min.

[0030] According to another particular characteristic, the ozone used isproduced from a dry carrier gas and in that the concentration of ozonein the carrier gas is between 80 and 160 g/m³ STP, and preferablybetween 100 and 120 g/m³ STP.

[0031] According to yet another particular characteristic, the pressureof the ozone-containing carrier gas during the bringing into contactwith the grains is between 200 and 500 mbar.

[0032] According to a third aspect, the subject of the present inventionis a specific installation intended for carrying out the method whichhas just been described.

[0033] This installation, of the type comprising means of storage andoptionally of mixing the grains, first means of cleaning the grains thusstored and optionally mixed, means of moistening the grains, means ofresting the grains thus moistened, second means of cleaning the grainsafter resting, means of grinding the grains, is essentiallycharacterized in that it comprises, in addition, means of bringing thegrains into contact with ozone produced from a carrier gas, arrangedupstream or at the level of the grinding means.

[0034] The invention will be understood more clearly, and other aims,characteristics and advantages thereof will emerge more clearly onreading the explanatory description which follows, made with referenceto the examples and to the accompanying schematic drawings givenentirely without limitation and in which:

[0035]FIG. 1 schematically illustrates a traditional method andinstallation for making flours;

[0036]FIG. 2 is a view similar to FIG. 1 of a method and an installationfor making flours in accordance with the present invention; and

[0037]FIG. 3 is a longitudinal sectional view of a contact reactor,specifically adapted for bringing the grains into contact with ozone inthe context of the present invention.

[0038] With reference to FIG. 1, a method and an installation for makingflours in accordance with the known state of the art will therefore befirst of all described.

[0039] Grains, for example wheat grains, obtained from an agriculturalsetting, are stored in storage silos respectively designated by thereference numbers 1, 2 and 3 in the example represented, and of whichthe number may be freely chosen to be perfectly adapted to theindustrial structure of the site and to the required autonomy.

[0040] These grains have, in the natural state, a residual moisturewhich is generally of the order of 13% in the case of wheat.

[0041] When it is desired to make flours from various wheat varieties,the grains thus stored are mixed in a mixing device 4.

[0042] The grains are then subjected to a first cleaning phase intendedin particular to separate the lightest particles, for example byblowing, using an appropriate device 5 well known to persons skilled inthe art.

[0043] After this first cleaning phase, the grains are moistened bysupplying water and are mixed.

[0044] The quantity of water supplied to the grains is adjusted suchthat the residual moisture of the grains, measured for example byhydrometry or by weighing, is optimum in order to carry out the millingoperation, that is to say of the order of 18%, in the case of wheat.

[0045] The grains thus moistened are subjected to a so-called “rest”phase in a silo 6 for a period generally of between 8 and 36 h.

[0046] After this rest phase, the grains are subjected to a secondcleaning phase, which may also be carried out by blowing with air, bymeans of an appropriate device 7.

[0047] This second cleaning phase makes it possible in particular torecover, as by-product, the envelopes of the grains (bran) used asanimal feed.

[0048] The grains thus moistened and cleaned are subjected to a grindingphase in a grinder 9 which may be of a type well known to personsskilled in the art.

[0049] The grinder 9 may be continuously fed, in a manner known per se,using an intermediate buffer silo 8.

[0050] With reference to FIG. 2, a method and an installation for makingflours in accordance with the present invention will now be described.

[0051] In this figure, the components identical to those described abovewith reference to FIG. 1 carry the same reference symbols.

[0052] The method in accordance with the present invention, whichconstitutes an improvement of the traditional method for making flourswhich has just been described with reference to FIG. 1, is essentiallycharacterized in that prior to or simultaneously with the grinding, thegrains are brought into contact with ozone produced from a carrier gasin a predetermined quantity and for a predetermined period.

[0053] Advantageously, the grains are brought into contact with theozone between the rest phase and the second cleaning phase, as indicatedabove.

[0054] In the embodiment represented in FIG. 2, the grains, afterresting, are introduced into a reactor 10 for treating with ozone (orcontact reactor) of which a currently preferred embodiment will bedescribed in greater detail later.

[0055] In accordance with the present invention, the contact reactor 10may be independently supplied with dry ozone, moist ozone or ozonatedwater.

[0056] The ozone is produced from a carrier gas advantageouslyconsisting of pure oxygen stored in a container 11.

[0057] Alternatively, the carrier gas may be produced from ambient air,filtered, compressed and dried at the dew point of between −50 and −70°C.

[0058] Alternatively still, the carrier gas may consist of a mixture, inany proportion, of pure oxygen and air which has been filtered,compressed and dried.

[0059] The ozonizer 12 thus makes it possible to produce a stream of dryozone-containing carrier gas having a dew point of between −50 and −70°C.

[0060] This dry gas stream may be used:

[0061] on the one hand, to directly supply the contact reactor 10 in acontrolled manner by a regulating valve 13; said gaseous stream beingconveyed to the contact reactor by the conduit 34;

[0062] on the other hand, for preparing a moistened ozone-containing gasstream, also intended to supply the contact reactor 10; and

[0063] finally, for preparing ozonated water advantageously intended tomoisten the grains after the first cleaning phase, and optionally foralso supplying the contact reactor 10.

[0064] The dry ozone-containing carrier gas produced by the ozonizer 12is moistened at room temperature conditions by passing through a liquidbed contained in a moistening column represented by the reference number15.

[0065] The dimensions of this column should be calculated to allowsufficient evaporation of water to ensure saturation at the pressure andtemperature conditions of the method.

[0066] In general, the ratio between the liquid height and the columndiameter may be between 1.7 and 2.5, preferably equal to 2.

[0067] The column 15 comprises, at its top part, an outlet for theozone-containing carrier gas thus moistened, which may be conveyed by aconduit 33 to the contact reactor 10.

[0068] The ozonated water may be produced from the dry ozone-containingcarrier gas coming from the ozonizer 12 by means of a dissolving reactorrepresented by the reference number 16.

[0069] In this reactor, the dry ozone is brought into contact with anaqueous phase in the form of bubbles whose diameter may be between 2 and4 mm.

[0070] These bubbles are created with the aid of porous disk-containingdevices, “herring-bone” devices comprising calibrated holes, or anyother device known to a person skilled in the art, such as a dissolvingturbine, a shearing turbine or a hydroejector with an intenserecirculation device.

[0071] In general, the higher the concentration of dissolved ozone inthe water, the shorter the residence time of the water in the dissolvingreactor 16.

[0072] Thus, the residence time of the ozonated water in the dissolvingreactor 16 will usually be between 2 and 12 min, preferably between 3and 6 min.

[0073] The conditions for dissolving the ozone in the water essentiallydepend on the concentration of ozone in the carrier gas, the pressurefor applying the ozone, the residual pressure in the gaseous ceiling, aswell as the size of the bubbles and the hydrodynamic regime at theinterface of the bubbles.

[0074] Persons skilled in the art will have no difficulty, during thecalculation of the dissolving reactor 16, in maximizing the parameterspromoting gaseous transfer toward the liquid phase, by preferablyadjusting the concentration of ozone in the gaseous phase, by increasingthe height of static water in the dissolving reactor, by increasing theresidual pressure in the gaseous ceiling, by increasing the overallinterfacial surface area for exchange, or by increasing the hydrodynamicregime at the gas-liquid interface (speed of the fluid, turbulence).

[0075] The ozonated water is extracted from the dissolving reactor 16 bya pump 17 and may be conveyed:

[0076] to the zone for moistening the grains, by a conduit 30;

[0077] to the reactor for bringing into contact 10 by a conduit 31; and

[0078] optionally, to the buffer silo 8 prior to the stage for grindingthe grains, by a conduit 32.

[0079] All these devices for supplying with moistened, dry ozone andwith ozonated water make it possible to ensure optimum treatment of thegrains, by combining a dry treatment with a wet treatment.

[0080] Such a combination is, for example, recommended in the context ofthe treatment of grains for the preparation of flours intended forbreadmaking.

[0081] In other cases, such as for example the preparation of animalmeals, or the preparation of flours for dairy products, a treatment byonly the dry route generally proves satisfactory.

[0082] The moistening necessary for the superficial impregnation of thegrains is preferably provided by the ozonated water serving during themoistening stage and additionally, optionally, by the adjustablecontinuous spraying into the reactor for bringing into contact 10 aswell as by the moisture provided by the moistened ozone-containing gas.

[0083] The ozonated water extracted from the dissolving reactor 16 mayoptionally also be conveyed to the storage silos 1, 2 and 3 forpremoistening of the grains.

[0084] It is also possible to effectively use the residual ozone presentin the carrier gas after reaction in the reactor for bringing intocontact 10, by extracting it with a compressor 22 and by conveying it bya conduit 35 to the storage silos 1, 2 and 3.

[0085] The residual ozone thus recovered allows a pretreatment of thegrains which may be advantageously combined with the abovementionedpremoistening.

[0086] In general, the reactor for bringing into contact 10 may bevertical and consist of a cylindrical or cylindroconical body with aconical base comprising an internal device providing a circulation and aresidence time of the grains in the reactor for bringing into contactwhich are sufficient to ensure optimum treatment with the ozone. Thebringing of the grains into contact with the ozone may be carried outcontinuously or batchwise in the reactor.

[0087] In general:

[0088] the overall residence time of the grains in the reactor forbringing into contact is usually between 5 and 70 min, and preferablybetween 15 and 40 min;

[0089] the degree of internal recirculation of the grains (that is tosay of the number of passes of the grains in the zone for bringing intocontact with the ozone) is usually of the order of 10 to 40, andpreferably of 20 to 30.

[0090] The internal recirculation may be provided by a jacketedArchimedean screw type device driven by an electromechanical deviceallowing the speed of rotation of the screw to be adjusted so as toprecisely provide the recirculation rate, which also depends on thethread and the diameter of the screw.

[0091] The contact reactor 10 is usually provided with a device fordischarging the reactive gas after reaction, with a system for sprayingozonated water supplied by the conduit 31, a safety device supplied withwater under pressure, a safety valve and a breaking disk.

[0092] At the bottom part, the contact reactor 10 comprises a device forintroducing and distributing the ozone-containing gas designed so as toensure distribution of the gas in the mass of grains with a sufficientspeed of injection to ensure good penetration of said gas into the massto be treated.

[0093] In general:

[0094] the speed of injection will be between 10 et 80 m.s⁻¹, preferablybetween 30 and 50 m.s⁻¹;

[0095] the concentration of ozone in the carrier gas will be between 80and 160 g/m³ STP (Standard Temperature and Pressure), preferably between100 and 120 g/m³ STP.

[0096] Moreover, the ozonation reaction being of the exothermic type,the body of the reactor for bringing into contact is usually providedwith a cooling device which makes it possible to maintain a constanttemperature inside said reactor for bringing into contact and in thereaction medium without a vertical or radial temperature gradient,during the time necessary for the reaction.

[0097] This effective cooling of the reactor for bringing into contactpromotes a safe use thereof, and allows precise control of the ozonationreaction.

[0098] The cooling device may, for example, be supplied with cold waterunder pressure or via a circuit of ice-cold water produced by arefrigerating set.

[0099] A currently preferred embodiment of the contact reactor 10specifically adapted for optimum use of the method in accordance withthe invention has been represented in FIG. 3.

[0100] This reactor for bringing into contact essentially comprises acentral endless screw 36 driven by a variable speed geared motor 37 andsurrounded by a central jacket 38 delimiting the preferred zone forbringing the grains into contact with the ozone.

[0101] The central jacket 38 is positioned relative to the walls of thecontact reactor by means of a centering device 39 well known to a personskilled in the art, and comprises cooling means which make it possibleto cool the reacting mass and to avoid radial temperature gradients.

[0102] The central screw 36 is positioned and centered inside thecontact reactor 10 by components 40 and 41 known to a person skilled inthe art, positioned at the top part and at the bottom part,respectively, of the contact reactor and ensuring imperviousness of thereactor.

[0103] Moreover, the contact reactor 10 comprises a supporting component42 designed to support and block the contact reactor canceling therotating torque generated by the movement of the screw.

[0104] At the bottom part of the contact reactor 10, at the level of thebase cone, there are inserted devices for injection of theozone-containing gas such as nozzles represented by the reference number43, which are advantageously radially arranged externally to the jacket38 to allow optimum penetration and distribution of the gas into thebulk of the grains to be treated.

[0105] In general, these injection devices are arranged, radially andexternal to the jacket 38, at a distance of between 0.17 d and 0.8 d andpreferably between 0.3 d and 0.67 d, where d represents the distanceseparating the external wall of the jacket 38 from the internal wall ofthe contact reactor 10.

[0106] The number of injection nozzles 43 will be chosen such that thespeed of ejection of the ozone is between 10 and 80 m/s, preferablybetween 30 and 50 m/s, and this number of nozzles will be generallybetween 15 and 85, preferably between 20 and 40.

[0107] The body of the contact reactor 10 as well as the base cone 44are advantageously cooled by means of an external cooling device whichmay, for example, consist of a conventional “water jacket” type deviceor of a circuit consisting of female molds ensuring capturing of theheat flow from the reaction mass and discharging it outside.

[0108] This cooling device will be advantageously provided with controlmeans such as a flowmeter, a counter, and the like, which are well knownto a person skilled in the art.

[0109] At the top part, the reactor for bringing into contact comprises:

[0110] a device 25 for introducing the grains to be treated;

[0111] a safety valve 46;

[0112] a disrupting disk 47;

[0113] a disk for extraction of the residual gas 48;

[0114] a disk for supplying with water (fire safety) designated by thereference number 26;

[0115] a device for supplying with ozonated water allowing possibleadjustment of the moisture of the grains during treatment.

[0116] The contact reactor 10 may be equipped, in a manner known per se,with means for controlling the temperature and the pressure, designatedby the reference numbers 49 and 50, respectively.

[0117] The endless screw 36 is advantageously equipped, in its bottompart, with scraping arms 51, preferably 4 in number, designed anddistributed to ensure a constant and homogeneous torque, to promotemixing of the grains, to ensure their migration to the center of thecontact reactor and their distribution by the endless screw.

[0118] The materials constituting the body of the contact reactor 10will be chosen so as to ensure resistance to abrasion and to oxidationgenerated by the presence of ozone at high concentration. Such amaterial may be, for example, stainless steel, known to a person skilledin the art.

[0119] In general, it has been observed that decontamination of thegrains is all the more effective if the renewal of the interfacialsurface area for exchange (grains-reactive ozone) was intense, and ifthe overall accessibility was maximized.

[0120] The contact reactor 10 should therefore be advantageouslydesigned to perfectly correspond to these parameters, ensuring effectivemixing of the grains and an optimized degree of recirculation of thelatter in the zone for treating with ozone.

[0121] The degree of recirculation essentially depends on the endlessscrew thread, its filling rate which depends itself on the size of thegrains and the speed of rotation of the endless screw.

[0122] In general, it has been observed that the following parameterslead to the best results:

[0123] “screw diameter/reactor diameter” ratio: between 0.1 and 0.5,preferably between 0.25 and 0.35;

[0124] “screw thread/screw diameter” ratio: between 0.4 and 1.1,preferably between 0.6 and 0.8;

[0125] screw filling rate: between 15% and 95%, preferably between 55%and 82%;

[0126] speed of rotation of the screw: between 50 and 200 rpm,preferably between 80 and 120 rpm with the possibility of variation inthis range so as to correspond to the geometry and to the variablediameter of the grains to be treated;

[0127] “useful reactor height/reactor diameter” ratio: between 1.1 and2, and preferably between 1.3 and 1.6;

[0128] “jacket height/diameter” ratio: between 1.4 and 2.2, preferably1.5 and 1.8;

[0129] “internal diameter of the jacket/reactor diameter” ratio: between0.1 and 0.5, preferably between 0.25 and 0.35;

[0130] angle of the base cone between 60° and 120°;

[0131] “total reactor height/reactor diameter” ratio: between 1.5 and 5,preferably 2.2 and 3.2.

[0132] The first trials for carrying out the method in accordance withthe present invention made it possible to demonstrate a considerableimprovement from the microbiological point of view in the quality of theflours obtained, compared with the use of a traditional method.

[0133] Thus, it was observed that the method in accordance with thepresent invention makes it possible to practically eliminate anymicrobiological contamination, in particular as regards mesophilicaerobic flora (M.A.F), the total coliforms, molds and yeasts.

[0134] The results obtained by the conventional methods for evaluatingthe abovementioned microbiological criteria on control samples(traditional method) and samples treated by the method in accordancewith the invention have been summarized in table A.

[0135] These results demonstrate the very high food safety level whichthe method in accordance with the present invention makes it possible toobtain. TABLE A MAF Control 22 000 000 Reduction: 99.90% Treated 13 000Total coliforms Control 2 800 000 Reduction: 99.90% Treated 900 MoldsControl 80 000 Reduction: 99.85% Treated 120 Yeasts Control 200 000Reduction: 99.80% Treated 310

[0136] Other trials were also carried out to evaluate the influence ofthe method in accordance with the present invention on the destructionof mycotoxins and in particular of ochratoxine A in wheat.

[0137] The results obtained by HPLC equipped with fluorimetric detectionbetween a control batch and a batch treated by the method in accordancewith the invention are the following:

[0138] Control batch: 39.80 μg/kg

[0139] Treated batch: 2.5 μg/kg

[0140] which corresponds to a reduction of the order of 94%, making itpossible to obtain a perfectly satisfactory product from the point ofview of the required food quality standards (standard: 5 μg/kg).

[0141] Other trials also demonstrated the value of the method inaccordance with the present invention on the reduction of contaminantsresulting from the use of pesticides.

[0142] A reduction of about 80% in the content of Chlorpyriphosmethyl (apesticide generally used in the case of wheat) was thus observed, thusleading certainly to a product which is perfectly acceptable from thepoint of view of the current food standards.

[0143] To demonstrate the technological qualities of the flours obtainedby the method of the invention, conventional breadmaking tests wereused, such as the determination of volume, smoothing, elasticity,porosity, firmness, stickiness, of the color and absorption of water.

[0144] The characteristics of the following 5 breadmaking batches werethus evaluated:

[0145] 2 control batches for which the grains were not treated withozone (batches Nos. 1 and 2);

[0146] 1 batch ozonated at a rate of 5 g/kg of grains immediately aftermoistening, and then allowed to rest for 24 hours before milling (batchNo. 3);

[0147] 2 batches moistened beforehand, allowed to rest for 24 hours, andthen ozonated, one at a rate of 5 g/kg of grains and the other at a rateof 4 g/kg of grains (batches Nos. 4 and 5 respectively).

[0148] For this evaluation, the following thirty criteria, grouped into3 classes, were first of all taken into account:

[0149] 1) Dough

[0150] kneading: consistency, stability, smoothing at 10°, smoothing,stickiness

[0151] molding: extensibility, elasticity, firmness, tearing, stickiness

[0152] proofing: activity, stickiness, stability in the oven (mini-maxi)

[0153] 2) Bread

[0154] crust: color, thickness, crispness

[0155] blade cut: slash in loaf (mini-maxi), evenness (mini-maxi),tearing (mini-maxi);

[0156] development: transverse section (mini-maxi), volume

[0157] 3) Crumb

[0158] color

[0159] cell formation

[0160] elasticity

[0161] odor/taste

[0162] A score of 0 to 5 was used for each criterion. It was found thatthe criteria for the batches according to the invention (3 to 5) werecomparable for all the criteria for the control batches.

[0163] Another evaluation criterion was then used which is the P/L ratioobtained from the conventional Chopin alveogram.

[0164] The applicant observed that by treating the grains with ozonebefore milling, the doughs made from the flours obtained by the methodof the invention had a completely modified alveogram.

[0165] The results obtained showed that the increase in the ozone zoneapplied during the treatment of the grains is perfectly correlated withan increase in strength and a decrease in extensibility.

[0166] Thus, by virtue of the method of the invention, it is possible tochoose and to control the increase in the P/L ratio for a given flour bythe choice of the level of treatment of the grains with ozone and by thepreliminary moistening of the grains with water, ozonated water or amixture of the two.

[0167] Most particularly, depending on the variety or the climaticconditions, it is thus possible to improve the quality of the flour (asin the case of an excessively extensible flour).

[0168] The results have also demonstrated the fact that by using a flourobtained from grains previously treated with ozonated water:

[0169] the dough used for making products which do not rise excessivelyduring baking, such as sweetened products of the English or Genoesefruitcake type, does not decrease again after baking, and does notexhibit the characteristic phenomenon of collapse often observed. Thequantity of ozone used is preferably at least 8 to 20 g of ozone/kg ofgrains, a quantity of 10 g of ozone/kg of grains being advantageouslypreferred;

[0170] the mixes for coatings (such as donuts, breadcrumb dressing, andthe like) do not exhibit the disadvantages observed during the use ofconventional flours which are the formation of vesicles or cracks at thesurface of the products. By contrast, the surface of the mixes obtainedaccording to the present invention have a homogeneous monolithicappearance, without the formation of vesicles, because of thepossibility of allowing the trapped baking gases to gush to the surface,such that the visual appearance is considerably improved;

[0171] the doughs used for the industrial manufacture of doughs and ofbreadmaking products, which are naturally too extensible, are capable ofabsorbing a volume of water which is higher than the usual conditions.The quantity of ozone used is preferably 3 g of ozone/kg of grains.

[0172] Finally, it was observed that it was possible to improve thealveometry without substantially modifying the W value (P/L ratio) ofthe doughs made from the flours obtained from grains previously treatedwith an ozone-containing gas by the dry or wet route, or after priormoistening with water or with ozonated water, and for a treatment rateof between 2 and 8 g of ozone/kg of grains, preferably between 3 and 5g/kg of grains.

[0173] The method which has just been described has very many advantagesamong which there may be mentioned in particular:

[0174] the simplicity of implementation, since this method perfectlyfits into the methods and installations for making flours which arecommonly used;

[0175] the food safety of the flours obtained; the combination of a dryand wet treatment making it possible to avoid the reviviscence of thestrains present at the periphery of the tegument during the rest phase,while preserving, or even improving, the technological qualities of theflours obtained.

[0176] This method makes it possible, in addition, to obtain by-productsof milling (bran) free of contamination, and the digestibility of whichwas found to be thereby improved.

1. A method for making flours having a high food safety level comprisingthe grinding of grains previously cleaned and moistened, characterizedin that, prior to or simultaneously with said grinding, said grains arebrought into contact with ozone produced from a carrier gas, preferablyin a quantity of between 0.5 and 20 expressed in grams of ozone per kiloof grains.
 2. The method as claimed in claim 1, characterized in thatthe period for which the grains are brought into contact with the ozoneis between 5 and 70 min, and preferably between 15 and 40 min.
 3. Themethod as claimed in claim 1 or 2, characterized in that the ozone usedis produced from a dry carrier gas and in that the concentration ofozone in the carrier gas is between 80 and 160 g/m³ STP, and preferablybetween 100 and 120 g/m³ STP.
 4. The method as claimed in one of claims1 to 3, characterized in that the pressure of the ozone-containingcarrier gas during the bringing into contact with the grains is between200 and 500 mbar.
 5. The method as claimed in one of claims 1 to 4,characterized in that the water serving for moistening the grains istreated beforehand with ozone.
 6. The method as claimed in one of claims1 to 5, characterized in that the ozone used is produced from a drycarrier gas and from a moistened carrier gas and in that this treatmentis optionally supplemented with the bringing of the grains into contactwith ozonated water.
 7. The method as claimed in one of claims 1 to 6,characterized in that the bringing of the grains into contact with theozone is carried out continuously or batchwise in a vertical contactreactor comprising a device for internal recirculation of the grains. 8.An installation for carrying out the method for making flours as claimedin one of claims 1 to 7, of the type comprising: means of storage (1, 2,3) and optionally of mixing (4) the grains; first means (5) of cleaningthe grains thus stored and optionally mixed; means of moistening thegrains; means of resting (6) the grains thus moistened; second means (7)of cleaning the grains after resting; means of grinding (9) the grains,characterized in that it comprises, in addition, means (10) of bringingthe grains into contact with ozone produced from a carrier gas, arrangedupstream or at the level of the grinding means.
 9. The installation asclaimed in claim 8, characterized in that the means of bringing thegrains into contact with the ozone mentioned above are arranged upstreamof the grinding means and comprise a vertical contact reactor (10)comprising a device for internal recirculation of the grains preferablyconsisting of an endless screw (36) surrounded by a jacket (38).
 10. Theuse of the flours obtained by the method as claimed in one of claims 5to 7, for making sweetened products of the English or Genoese fruitcaketype.
 11. The use as claimed in claim 10, characterized in that thequantity of ozone used is 8 to 20 g/kg of grains, and preferably 10 g/kgof grains.
 12. The use of flours obtained by the method as claimed inone of claims 5 to 7, for the industrial manufacture of doughs andbreadmaking products.
 13. The use of flours obtained by the method asclaimed in one of claims 5 to 7, for the industrial manufacture ofdoughs and breadmaking products.
 14. The use as claimed in claim 13,characterized in that the quantity of ozone used is 3 g/kg of grains.